Posted
by
samzenpus
on Monday July 29, 2013 @09:30AM
from the throwing-it-out-there dept.

cylonlover writes "People have been shooting things into space since the 1940s, but in every case this has involved using rockets. This works, but it's incredibly expensive with the cheapest launch costs hovering around $2,000 per pound. This is in part because almost every bit of the rocket is either destroyed or rendered unusable once it has put the payload into orbit. Reusable launch vehicles like the SpaceX Grasshopper offer one way to bring costs down, but another approach is to dump the rockets altogether and hurl payloads into orbit. That's what HyperV Technologies Corp. of Chantilly, Virginia is hoping to achieve with a 'mechanical hypervelocity mass accelerator' called the slingatron."

Well they have virtualized the physics. Despite the claims on their website cyclotrons oscillate at a fixed frequency because the path length for each semi-circle increases in direct proportion to the velocity i.e. the time to turn through 180 degrees remains fixed. In fact this was why cyclotrons could only be used for heavy particles like protons and atomic nuclei - put an electron in there and it would become ultra-relativistic and so the half-period would increase because the velocity was essentially fi

True, but the moon lacks resources crucial for life... like, for example, air. We haven't yet figured out how to create a sustainable self-enclosed biome. The only place that exists so far is on this rock we call Earth... so they can try and declare independence, and it'll last about as long as it takes for them to run out of supplies.

Just to clarify: it's not that the person with the most dollars gets his guy into office. The system currently allows someone to contribute money to all possible candidates and without those candidates knowing that you paid their opponents as well. Since you have paid all possible parties, your views are guaranteed to be represented regardless of who wins. And then a whole bunch of people will call the voters stupid for electing these guys when the fact of the matter is that all sides were bought because the system is corrupt. I hate to sound cynical, but at this point, it really doesn't matter who you vote for in federal elections.

Sorry, but given a "plurality rules" voting system, that won't work. If a majority of votes were required, that would be a defensible tactic. This is why I favor either Condorcet voting or IRV (Instant Runoff Voting.).

I will agree that there is no perfect way of counting votes, but plurality rules is worse than most of the options. In fact I would consider it significanlty worse than slection by lottery.

Replying to my own post... I thought about it a bit more, and you could probably hurl raw materials or durable parts up to space with this and then use on-orbit lasers to correct its final orbit. At that point, you can scoop it up and put it where you need it.

It’s questionable whether any rocket system could survive such stresses and there’s certainly no chance of a slingatron being used on a manned mission because it would turn an astronaut into astronaut pudding. Only the most solid state and hardened of satellites built along the lines of an electronic artillery shell fuse would have a chance of survival. The developers say that a larger slingatron would reduce the forces, but even with a reduction by a factor of 10,000, it would still be restricted to very robust cargoes. This makes it mainly attractive for raw materials, such as radiation shielding, fuel, water, and other raw materials.

Why not just use it for propulsion? It's quite easy to vary the speed objects are launched at, and the machine gets cheaper for smaller payloads, so just put your spaceship into orbit conventionally and then bombard it with a stream of tiny metal pellets to get it moving. Keep the collision speed constant by firing the pellets faster as the ship accelerates, and you can build up speed without carrying reaction mass.

Even better, use something like those magnetic balls you can buy as desk toys, and your ship

Lets say you make a spherical tank that holds oxygen and try sending to the ISS. You could fire it at a precise orbit to get near the space station, but unless the tank has some kind of maneuvering jets, you will need to chase it down and capture it. The tank most likely will be spinning rapidly and be a pain to capture.

A surprisingly large amount of stuff sent into low earth orbit and even geosynchronous orbit consists of fuel and oxidiser. The Shuttle launched with over 14 tonnes of manoeuvering fuel and oxidiser on board for the OMS and RCS motors. That's 14 tonnes that couldn't be dedicated to payload, food, water etc. Similarly a geosynchrononous satellite weighing 6 tonnes will be carrying two or three tones of fuel and oxidiser so it can maneuver into its final orbit and allow it to maintain station for a decade or more. Some GEO birds have been decommissioned when they nearly ran out of fuel, not because they broke down or became obsolete.

Using a slingshot or other brute-force technique to put tanks of fuel and oxidiser into orbit cheaply could well be worthwhile; robot tugs could collect them into a tank farm of some kind in a higher orbit and then deliver fuel and oxidiser to various vehicles as needed rather than them having to lift their entire fuel and oxidiser loads along with delicate electronics, structural components for Mars landers, fleshy meatbags etc.

Taking stuff into space requires a huge amount of energy. Right now, the stuff we sent into space has to carry its own energy, stored in fuel. Because so much energy is needed, lots of fuel is needed. But fuel is heavy, so even more energy is needed.

Externalizing the energy source for what gets sent into space can severely lower costs of getting stuff up there. I don't know if a slingshot is the best way to do it, but at least it's thinking in the right direction.

It's kind of difficult to think back that far but in the 70s space launches were complicated things, not run-of-the-mill operations like today. One of the constraints that resulted in the Shuttle design was the necessity to launch the crew and payload in one shot. The idea of launching two or three individual payloads and crew capsules within a few days of each other and have them make rendezvous in orbit was beyond the capability of anyone at the time. The Shuttle was basically a variant of the one-shot Ap

It’s questionable whether any rocket system could survive such stresses and there’s certainly no chance of a slingatron being used on a manned mission because it would turn an astronaut into astronaut pudding.

True but pointing out how a solution doesn't solve every aspect of every problem is what gets a post modded up around here. This reinforcement of short-sightedness keeps rearing it's ugly head with nearly every article. Thus even people who know better are still prone to postings such as this just because they know it'll be modded up. The cycle continues and we help to breed a new generation of cynics who don't think that things getting a little better today is a worthwhile goal if it's not the future promised to them by the most optimistic sci-fi stories.

Payload on a ballistic arc is worthless (**) unless you can do a subsequent burn at apogee to raise the perigee above the atmosphere. They are unlikely to be able to build a rocket that is hardened enough to survive launch, but is large enough and has enough thrust to raise perigee before it and the payload reenter and burn up.

(** Outside of lobbing nukes at people.)

That said, this might be more useful on a low-gravity, atmosphere-free body like the moon, where you can build the spinner much larger, and launch at a much more horizontal trajectory (improving efficiency, and making interception easier, via an orbital tether). So as long as these guys aren't wasting my money, I'm happy for them to waste their own time and money to develop and prove version 0.01a of the technology.

They are unlikely to be able to build a rocket that is hardened enough to survive launch, but is large enough and has enough thrust to raise perigee before it and the payload reenter and burn up.

Why would you assume that? They built nuclear weapons in the 1950s that could survive being launched from a howitzer, there were (are?) missiles that were launched from naval 5 inch guns. The advances in engineering and materials science in the last half century would imply (to me anyway) that this shouldn't be an insurmountable obstacle.

And yet, between the ones who want to terraform Mars tomorrow (which I will note that GP is not), and the people like you who want to kick the can down the road forever, we will make progress. Just as GP said.

One important thing to note is that astronauts will need cargo for the foreseeable future. Just because it doesn't look like we'll ever be able to Sling people doesn't mean it's not useful to manned spaceflight.

A kickstarter for a version that'll launch 1lb loads up to a small portion of the speed of sound. You're not getting anything in to orbit on the back of this, just helping this guy make a marginally more convincing case to bigger funding agencies. Although if the physics and engineering made sense, I'm not sure why a marginally larger prototype than the ones they already have is needed.

Anything that can launch stuff into orbit can probably also be tweaked to drop stuff literally anywhere in the world.

I don't think there's any probably to it... if you can get something into space, you can get it pretty much anywhere you like if you can figure out the flight mechanics of it. Which is why when people do any rocket testing, people are paying close attention since a rocket and an ICBM are pretty similar -- if you can do one you can do the other.

At those speeds, even a few kilos of mass is going to hit anything with some pretty serious force.

The mechanics are a solved problem. Large artillery pieces already need to correct for the rotation of the earth, and all artillery needs to correct for atmospheric conditions that vary with altitude. This device would just need to correct for a lot more of it.

This is just a really big howitzer, and behaves exactly the same as one from a ballistics perspective.

there are a couple things to mitigate that problem, if it is going generally up and the onboard electronics come online (similar to way artillery fuzing is activated after launch), self destruct could be sent

for failure during acceleration, destroy the machine in such a way the projectile is guaranteed to ram into bedrock down or off to side

most of world uninhabited, for the edge case of failure in acceleration right before projectile leaves, and on board self-destruct can't be activated, then you're in the

They specifically say it isn't for delicate things. The concept they're using is putting bulk building materials in space cheaply and saving the 'delicate' stuff like people for the expensive and less taxing delivery of rockets.

Out of curiosity, why aren't mass drivers feasible for this sort of thing? You could build one up a mountainside near the equator - something like Mt. Chimborazo (6200+ meters) and drastically reduce the amount of fuel needed to get anything into space. By making the thing several kilometers long, you'd also massively lower the material strains on any craft (you probably still couldn't send humans up, but you'd have far less limits on how sensitive your cargo could be.)

The slingshot sounds like an extremely limited tool - you'd still need a high degree of complexity for things like guidance systems and engines, because of drag you probably couldn't launch anything right into space without at least a partial boost. A mass driver would only get your cargo up to equivalent speeds once it got to the "muzzle", which would ideally be located at very high altitudes with thin air...

Well, for 2 reasons – and the reasons apply to all space guns – including mass drivers and Slingatron.

I am not a physicist, but I have been told that the orbital path for any projectile fired from a space gun will pass though earth – which is a fail. So you still need rockets in space to get to a viable orbit, and rockets are fragile things.

The applied engineering is thin on the ground and the upfront costs are massive. There is a large gap between theatrically possible verse practical app

Lets assume orbital velocity is enough and there are no loses to the atmosphere. So we need about 7500m/s. Now we can see what acceleration we need for a track "several ks long". a=v*v/(2s) =14062m/s^2. Or 1433 g's. Best not to be a fragile meat bag. Lets assume we can make a 20km track. Well that is 10x longer so we get one tenth the acceleration. Or only 140g's. 200km seems a better 14g's. Of course this 14 g's last for 53 secs. One hell of a ride.

Real numbers would be much worse. For a muzzle V of 10km/s they are 77% worse.

The slingshot is in fact a far less realistic approach, we could build a mag train with these specs if we were so inclined to sink the billions it would cost to do so. But the slingshot has very large forces between the "track" and the projectile while still requiring a massive track that all moves!

Personally if we are going to dream then a launch loop is my preferred "rockets suck" alternative.

By the way Rockets don't suck. They do what they do well. Far better than anything else at this point. There is no reason they have to be as expensive as they currently are.

They're going to launch it from the surface at orbital velocity? It would burn up from the air friction inside the Slingitron itself before hitting orbital velocity. If it didn't (i.e. it was a vacuum inside the Slingitron) - it would as soon as it hit the outside air. Meteorites and returning spacecraft do this (in the opposite direction) when the reenter the Earth's atmosphere. Watch how much the atmosphere slows them down (and burns them up). Why wouldn't this happen from a Slingitron launch? This issue was never even addressed in the video.

Perhaps they could coat the payload with an ablative heat shield? And presumably they would build the thing at high altitude to avoid the "thick" air below. Nevertheless, you're right that they'd have an "uphill battle" to reach orbit this way.

There have been experiments to shoot things into space using cannon (for research) since at least Project Harp [wikipedia.org] of the 1960's. They tended to have funding problems, leading Gerald Bull [wikipedia.org] (their chief proponent) to accept money from Saddam Hussein to build a supergun using the same technology, which lead to his assassination.

Have they actually studied physics? This project is so bogus on multiple levels:
1) It's much easier to use a linear accelerator. It won't have to deal with tremendous loads from centrifugal forces, for one thing.
2) Acceleration will be murderous for anything that's not a solid material.
3) And finally, it still won't work even if a payload is accelerated to orbital speed. That's because the payload would re-enter the atmosphere and return to the point where it left the accelerator at the end of its first orbit - that's simple freaking orbital mechanics. And you need quite a bit of delta-v to lift the perigee high enough to avoid it, which requires a rocket with an engine, see 2) why it's not feasible.

3) And finally, it still won't work even if a payload is accelerated to orbital speed. That's because the payload would re-enter the atmosphere and return to the point where it left the accelerator at the end of its first orbit - that's simple freaking orbital mechanics.

TFA points out that it will have to have an orbital insertion motor on board.

The acceleration would liquefy it into a long stream, and the deceleration would vaporize it within meters of the bore.

While it accelerates it would undergo incredible centripetal force along one axis, which would tend to force the material along the other axes (pumpkin pancake). In the air pumpkin juice would be decelerated along one of the long axes, causing it to pancake up again in a different direction briefly before it was completely reduced to plasma due to interaction with the air.

How many people laughed at all the rednecks creating weird contraptions to hurl pumpkins down a harvested field in Discovery channel? Now who is laughing, eh?
When space travel is commercialized and you are crammed into the economy class seat of the commuter plane to mars, you may have to thank Bill "1 gallon" Schwarzenhammer, winner of Pumkin Chunkin 2021, who was the first one to hurl a pumpkin all the way to Moon, more known for his ability to gulp down 1 gallon of beer without pausing for breath.

And since the vacuum insulated the heat, it matter a whole lot less. Who cares if something is hot, if the only possible way it could be bad is if an astronaut took off his suit in space and then touched it.

So in the end this is just another Kickstarter Slashvertisement from two guys who want you to pay them to keep screwing around with random, unworkable ideas rather than actually work for a living. At least they aren't standing at the end of the exit ramp begging for handouts.

Right. What they have now as a demo underperforms most handguns in muzzle velocity. What they propose to build with Kickstarter funding has the performance of a low-end artillery piece and is an order of magnitude below what's needed to get to orbit.

Unless they can show that their idea scales better than the various space gun [wikipedia.org] schemes, this is a lose. The HARP space gun reached about half of the necessary velocity in the 1960s. A space gun is quite possible, but can't put something in orbit directly witho

Certainly a constraint, but one key difference. It gets less resistive as you go, the opposite of coming in. At 6 kilometers/sec, you're out of the really dense atmosphere pretty quickly.

That is true, but in general you'd need a much larger heat shield for this than you'd ever need for re-entry of an equivalent payload. With re-entry the highest speed is at the lowest air density. With a mass driver the highest speed is at the highest air density.

Sure, you'll get through it quickly, but that just means that the amount of power being dissipated as heat is astronomical.

I'd think the G forces from atmospheric drag would be incredible as well for the first few seconds.

Certainly an interesting material/chemical engineering problem. Another key difference is the duration of exposure. If you have something with a sufficiently high resistance but low durability it may still be adequate since it's job is done quickly. If I remember, the shuttle tiles were a problem because they were both fragile and had to be stable for multiple minutes in plasma conditions.

I also don't know if you could 'shape' the payload. If the centrifuge would make you have to shoot roundish obj

When the projectile is moving at about 7,000 miles per second.. is it not going to heat up and vaporise when it encounters friction from the atmosphere and the slingatron? How hot will it get, and if the contour changes are irregular, will the projectile not deviate off its expected path? I think it makes more sense to build a super gun on Mount Everest, or use a stratospheric aircraft to provide a lifting platform to get a rocket out of dense atmosphere.

[Emphasis Added]

.037c? That seems rather excessive when trying to get to LEO. Then again, it will get you to the moon in 34 seconds and to Mars in less than six hours -- assuming you don't want to stop and look around -- then you'll need to decelerate.

I assume you mean 7 miles per second (escape velocity on a body the size of the earth is ~25,000 miles/hour) or are in a *really* big hurry.

At 7000 miles per second (11,000 km / sec, or 4% of the speed of light), you would expect a strong emission of 1 MeV gamma rays and an energy release in the megaton range for a 100 kg payload; basically you would have created the kinetic equivalent of a nuclear bomb.

At 7000 miles _per hour_, not so much. Project HARP [wikipedia.org] fired 8000 miles per hour payloads in the 1960's.

I've thought about mounting a gigantic railgun on the eastern flank of Mount Kilimanjaro. You'd need to lengthen the barrel partly into the earth to give a longer run-up. Keep the barrel evacuated -- you can probably use a plasma window at the exit point to keep the atmosphere out. (although I'm not certain a plasma windows would work terribly well with a large aperture -- can anyone tell me?)

The tricky part is you'd need to accelerate your projectile at over 5000 gravities for the ~ 0.3 seconds it would ta

For that matter, you could fill the last fourth of the tube with hardened concrete, and it *still* wouldn't make a calculable difference to the stresses on the cargo. We're talking about a lot of stress on that cargo.